Nowadays, increase in recording density of disks serving as storage media are promoted, in a field of disk storage apparatuses such as hard disk drives (hereinafter simply referred to as a “disk drive”). In a disk drive, a number of cylinders (tracks) including servo areas (hereinafter referred to as “servo sectors”), on which servo information are recorded, are arranged radially on the disk. The servo information is positional information used to detect a position of the head on the disk, and includes address data including a cylinder number and a servo sector number.
In the meantime, a method for dividing servo information has been proposed to increase the recording density of disks. In the method, a cylinder code forming a cylinder number to identify a cylinder is divided and recorded among a plurality of servo sectors in the cylinder. Although the method reduces the size of each servo sector, the size of each servo sector can be more effectively reduced, by reducing an area for recording the servo sector number, as well as the cylinder number.